1. Field of the Invention
The present invention relates to a method for protecting proteins from denaturation which occurs when the proteins are frozen. Further, the present invention is relates to use of polypeptides for protecting proteins from such denaturation caused by freezing.
2. Description of the Prior Art
In the field of genetic engineering, biochemistry, food and pharmaceutical industries, and the like, various proteins including enzymes are commonly preserved by freezing.
Generally, proteins are known to change their high-dimensional structure upon freezing and thawing. When such denaturation of proteins associated with the freezing (occasionally called freeze denaturation hereinafter) occurs, protein activity may be decreased or completely lost, which causes problems in storing proteins.
Conventionally, in order to prevent such freeze denaturation of proteins, bovine serum albumin (BSA), glycerol, sugars, or the like are usually added to the proteins to be kept frozen for storage.
However, when the abovementioned additives are used, bovine serum albumin (BSA) is limited in its supply and generally very expensive. Further, serums derived from animals cannot sufficiently ensure the safety because of their possible risk of viral infection. Furthermore, glycerol, sugars or the like must be added at a concentration as high as 20% or so, which affects activity of proteins of interest. Further in this case, a process to remove the abovementioned additives may be required after freezing and thawing depending on the kind of proteins or use thereof, which may require a complicated removing step or may increase the cost. Also for this reason, use of these additives has not been desirable.
Accordingly, there is still a need for means to prevent freeze-induced decrease in protein activity or inactivation of proteins during freezing/thawing cycles.